Sinapyl alcohol

Fresh root samples were ground into fine powder with liquid nitrogen using a sterilized pestle and mortar. Fine powders (0.2 g) were homogenized in an ice-cold extraction buffer (15 ml) as described by Ana and Ian (2000) (link). The concentration of PAL, CAD, and POD in the supernatant (0.2 ml) was measured at 290, 340, and 470 nm, respectively, using a MultiScan Go (Thermo Fisher Scientific, United States) spectrophotometer. Concentrations were calculated for every 0.01 g of root tissues based on an extinction coefficient (€) value derived as follows: PAL (€) = 2.6323 × 10^-6 (M^-1) (cm^-1); CAD (€) = 2.5685 × 10^-6 (M^-1) (cm^-1); and POD (€) = 1.2349 × 10^-6 (M^-1) (cm^-1). The (€) value of PAL, CAD, and POD was generated using L-phenylalanine, sinapyl alcohol and guaiacol, respectively (Sigma–Aldrich, United States).

Ultra-pure water (18 mΩ) was obtained from a Milli-Q water purification system (Millipore Co., Ltd., Milford, MA, USA). High-performance liquid chromatography (HPLC)-grade methanol, acetic acid, and 56 analytical standards, including catechinic, scopolin, chlorogenic acid, epicatechinic, vanillic acid, caffeic acid, purerarin, syringic acid, daidzin, glycitin, scopoletin, eriocitrin, umbelliferone, p-coumaric acid, dihydroquercetin, sinapic acid, genistin, liquiritin, ferulic acid, salicylic acid, rutin, isoferulic acid, m-coumaric acid, naringin, hesperidin, resveratrol, xanthotoxol, silydianin, sinapyl alcohol, o-coumaric acid, liquiritigenin, kaempferol, 2’-hydroxygenistein, eriodictyol, daidzein, psoralen, glycitein, quercetin, didymin, bergaptol, naringenin, luteolin, cinnamic_acid, hesperetin, genistein, bergapten, diosmetin, isoliquiritigenin, coumestrol, sinensetin, formononetin, medicarpin, imperatorin, biochanin A, tangeretin, and rotenone (displayed in Table S2), were purchased from Sigma-Aldrich Co., Ltd. The stock solutions of these authentic standards were 10.0 mg of each standard dissolved in 10 mL methanol. Then, the stock solutions were diluted to various concentrations before analysis. All stock solutions were sealed with Parafilm^® and stored in a −20 °C freezer.

Commercial food grade bamboo poles obtained from Mount Huangshan, Anhui Province of China, were used in this study. 2-Hydroxyterephthalic acid (HTA), terephthalic acid (TA), conyferyl alcohol, sinapyl alcohol, D-xylobiose, vanillic acid, vanillin, gallic acid, 5-hydroxymethyl-furfural, D-cellobiose, D-cellotriose, glucuronic acid and guaiacol were purchased from Sigma Aldrich (USA). All other reagents were of analytical grade and used as received, if not otherwise specified.